Making fuels from atmospheric carbon dioxide
Can we meet the demand for kerosene, diesel and jet fuel, without contributing to the rapid increase of atmospheric greenhouse gas carbon dioxide (CO2)?
Potentially, the answer is "yes". By using direct air capture technology, an engineering firm in Canada have created an economic, carbon-neutral fuel by capturing CO2 from the atmosphere.
The method uses potassium hydroxide to remove industrial-scale quantities of CO2 from the air. And unlike other methods of CO2 capture, this new method can bring CO2 in from anywhere, and isn't limited only to power plants.
Gases being processed pass through a system where chemicals are used to bind and extract pure carbon dioxide.
"Carbon Engineering is commercialising direct air capture. That’s the process that takes the CO2 out of the atmosphere and makes a concentrated pure CO2 steam. And the primary application for that technology, from our point of view, is carbon neutral hydrocarbon fuel," says lead researcher David Keith from engineering firm Carbon Engineering.
Scientists have been working on ways to capture CO2 from the air for nearly 30 years. The stripped out CO2 can then be disposed of by liquefying and injecting it into underground aquifers. The price tag varies, and can reach as high as $1000 per ton of CO2 captured.
Now Keith and his team have taken things one step further by making it into fuel, and reducing the cost of the capturing process.
Carbon Engineering, located in British Columbia, have been able to develop a pilot plant capable of successfully capturing 365 tonnes of CO2 from the atmosphere per year. With this system, it would cost between $94 to $232 per tonne of CO2 captured.
"We are convinced that we can build it at large scale cheaply... we work very closely with the manufacturing of these huge cooling towers and while our structure is a slightly different shape it uses the same components, the same fans, the same packings as they do. So we think we understand the capital and operating costs of these system really quite well," says Keith.
The industrial scale design would be capable of capturing one million tonnes of CO2 per year, which is equivalent to the annual emissions of 250,000 cars, which sounds promising, but how do you make fuel from CO2? Hydrogen is extracted from water, and then combined with the captured CO2. This produces liquid fuels with a net zero carbon footprint, which would work in exisiting car engines.
"The application would be to basically allow that energy to power things like aeroplanes, or heavy trucks, or the heavy end of the transportation system that needs high-energy-density, storable fuels," says Keith.
In five years, Carbon Engineering is hoping to be able to produce at one plant 318,000 litres of liquid fuels per day, at a cost of approximately $1 per litre to consumers.
"Like lots of other things that end up really making an impact, this is not about some brilliant scientific innovation in a lab. This is about dedicated engineering over more than a 100 person-years of effort to just grind down a whole bunch of engineering details to bring something practical into the world."